Uncertainty of nitrate and sulphate measured by ion chromatography in wastewater samples

This paper presents an evaluation of measurement uncertainty regarding the results of anion (nitrate and sulphate) concentrations in wastewater. Anions were determined by ion chromatography (EN ISO 10304-2, 1996). The major sources of uncertainty regarding the measurements’ results were identified as contributions to linear least - square or weighted regression lines, precision, trueness, storage conditions, and sampling. Determination of anions in wastewater is very important for the purification procedure, especially the amount of nitrate in waste and potable waters. The determined expanded uncertainty was 6.1 % for nitrate anions and 8.3 % for sulphate anions. The difference between measurement uncertainties determined by the two methods, the weighted and linear least - square methods, is negligible. [...]

[9] International Standard ISO 5667-14:1999, Water quality-Sampling-Part 14: Guidance on quality assurance of environmental water sampling and handling, International Organization for Standardization, Geneve.

[10] European Standard EN ISO/IEC 17025: 2005, General requirements for the competence of testing and calibration laboratories, European Committee for Standardization, Brussels.